Compressed air is supplied from a pneumatic source to a pneumatic device, such as a pneumatic cylinder, through a pneumatic line, such as piping or a hose. The pneumatic source and the pneumatic device are connected to each other through the pneumatic line, thereby forming a pneumatic circuit. Compressed air to be supplied from the pneumatic source to the pneumatic device is regarded as “air-to-be-treated”, and the pneumatic circuit is provided with a filter for removing foreign matters, such as liquid, oil, and dust, contained in the air-to-be-treated.
Size of foreign matters to be removed depends on conditions such as an inner diameter of an air passage hole on a filter element. A filter has a form such as an air filter, a mist filter, or a micro-mist filter, depending on the size of the foreign matters to be removed.
This type of filter comprises a filter container and a cylindrical filter element disposed inside the filter container. The filter container is detachably attached to a port block. According to a filter described in Japanese Patent Application Laid-Open Publication No. 2012-232281, air-to-be-treated is supplied to an outside of a filter element of the filter, is filtered through the filter element, and flows from inside of the filter element to outside of the filter. In this filter, a deflector and a baffle are attached to respective ends of the filter element, and the filter element is attached to an opening portion of a housing by the deflector.